Applications requiring light energy and specifically laser energy may benefit from the use of solid state light sources such as laser diodes which are commonly available, reliable to operate and relatively cost effective as a laser energy source. Such devices may include a plurality of laser emitters in a single bar that emit laser light simultaneously in a common direction. In addition, multiple solid state or laser emitter bars may be disposed in a stacked configuration so as to generate even higher power levels. Typically the emitters of such solid state emitter bars are spaced from each other to allow sufficient cooling without the need for elaborate and expensive cooling systems.
Laser diode bars are often used for communication technology devices, medical applications and other applications where it is desirable to couple the output of all the emitters of a single solid state emitter bar or multiple bars in a stacked configuration into a single optical fiber or other optical conduit. The spatial distribution of the emitters of a bar or stack of solid state emitter bars can make coupling the output of multiple emitters challenging, particularly when coupling to a small diameter optical fiber.
While the use of a micro-lens array reduces the divergence angle among the longitudinally separated beams emanating from the emitters of a bar, a solid state emitter bar which incorporates several, transversely separated emitters requires that an objective lens or lenses having a large numerical aperture be used if the beam is to be concentrated into a usefully small spot. Large numerical aperture objective lenses tend to be expensive. The problem becomes even more difficult when more power is required than can be delivered by a single laser bar. If it is attempted to use two laser bars, the lateral separation of their beams adds to the difficulty.
As such, what has been needed are methods and devices for coupling the output of multiple emitters of a laser emitter bar or stacked laser emitter bar array while maintaining a high degree of brightness and coupling efficiency.